If you are going to Potsdam by train, it is certainly the best choice. The train station is just across the road (and river). The hotel is modern and the rooms are elegantly furnished.
If you are going to Poznan by car, the hotel is easy to find: it is the tallest structure in the outskirts of the town (and a bit of an eyesore). Finding the way to access the hotel is not obvious (maybe made worse by some roadworks) and parking was just a nightmare. There are two car small car parks, completely insufficient for the number of guests: the alternative was to park (illegaly) on the road or half a mile away. Also be aware of the sign at the entrance that indicates which of the two car parks is full: it sent us to the car park that was completely full, while the one that supposedly was full, actually had a couple spaces left. Eventually we got in the right car park and had to pay 9 euro for the pleasure.
It was also surprising that such a hotel did not have a swimming pool or jim (it was offering maps of local areas where to do jogging).
Staff were not the friendliest (although our complaints about the parking may have had something to do with it).
The room was nice and perfectly clean but a little small for two people with two bags.
If we were to go back to Poznan (very nice place, highly recommended!!!) we would probably shop around before going back to the Mercure.

We booked our stay at this hotel ahead of time for only 55 Euros for both of us in a double room for a night, which is a pretty good rate. The location is as good as it gets for me, as it is almost right across from train station, so it's only about a 5 min walk to get there (have to cross the bridge) (being close to the train station is my biggest priority, as I always like to walk and i visit many cities on my trips so im always arriving and leaving). It's about 20 mins into the city center or sansousci by foot, which I highly recommend doing by foot because Potsdam is a very cute little city and worth the walk through, even in winter (plus we ran into a very good bakery on the way doing so which was a much cheaper breakfast than at the hotel).

Very clean, a bit small but can't complain. Excellent hotel, would book again for sure for the rate we got.

Having visited Berlin on a few occasions I was not too concerned about the location of the Mercure Potsdam.The transport system is so spot on that even a hotel in Potsdam is only 15 - 20 minutes by RE from central Berlin.One warning would be to avoid the S Bahn train as it takes over 45 mins each way between hotel and city centre.
The hotel itself is absolutely in keeping with Mercure standards.The bathrooms have been renovated recently and flat screen tvs in the rooms add to the overall comfort level.
The main complaint would be the air con. or rather the Mercedes Benz 6 cylinder engine that drives it.It was over 35 C during the day and the room heated up like an oven .For some reason whoever designed the room placed the unit under the window and with the curtains closed to keep sunlight out any cold air generated disappeared behind the curtain.It was also impossible to sleep at night with the air con. on due to the noise generated by the unit.
Overall a good , inexpensive option even if the breakfast is a little overpriced at 15 Euros.

i booked through a german website and got a very competitive rate. arrived by train, was pleased to find the hotel near the railway station.

had a room by the elevator (ending *02), in which wlan did not work, even though i had explicitly asked for a room with wlan. had to switch rooms next day. the a/c was unable to take away steam caused by showering when there is not a proper bathroom door, so the atmosphere was very very damp.

there was a hidden catch in the wlan pricing scheme; for the cheapest/default price you can use it only between 18:00-09:00, even if you have paid for multiple days. daytime usage would have to be bought separately. regarding the breakfast, at 15€ the quality did not really match the price.

the biggest turn-off for me was the location; if your points of interest are east from sansoucci park, I would not recommend this hotel. also; there was a large construction yard next to the hotel, due to which the nearest bus-stops were closed.

however, for the competitive price (around half of what was stated at a billboard at the reception), this was decent. would not, under any circumstances, pay the stated price from my own wallet.